PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 545 
depth of its valves, particularly the brachial valve. It is also strongly costellate 
and has a deep sulcus and strong fold. It strongly simulates a robust form of 
Parastrophina with which it occurs. These features distinguish the species from 
any of the forms described herein, even O. gibbosa which is generally somewhat 
smaller, more sparsely costellate, and with both valves less deep. 
OXOPLECIA GOULDI Ulrich and Cooper 
Plate 103, C, figures 17-29 
Cliftonia gouldi DEcKER, Oklahoma Geol. Surv. Bull. 55, p. 42, pl. 13, fig. H (nomen nudum), 
1931. 
Cliftonia (Oxoplecia) gouldi Utricu and Cooper, Journ. Paleont., vol. 10, No. 5, p. 338, 
pl. 50, figs. 8, 15, 18, 19, 23, 28, 32, 36, 1936. 
Types.—Holotype: 91897; paratypes: 91898a,b; 91899; figured hypotypes: 
110876, 118010. 
Horizon and locality—Bromide formation (Pooleville member—O-oplecia 
gouldi zone) in Carter County, Okla.: At Rock Crossing of Hickory Creek, 
about center sec. 35, T.5 S., R. 1 E., Criner Hills ; NW4 sec. 26, T.5 S.,R.1 E.; 
NE# sec. 1, T. 2 S., R. 2 W, 3 miles east of Pooleville, Carter County. Same 
formation and member in Murray County, Okla.: 20 feet above the green shale 
on Spring Creek, N$ sec. 17, T. 2 S., R. 1 W., Murray County. 
OXOPLECIA HOLSTONENSIS Willard 
Plate 90, J, figures 62-64; plate 100, G, figures 30-34; plate 1o1, D, figures 23-43 
Oxoplecia holstonensis Wi1LLarD, Bull. Mus. Comp. Zool., Harvard Coll., vol. 68, No. 6, 
p. 287, pl. 3, fig. 17, 1928. 
Shell of about medium size for the genus, nearly circular or slightly elliptical 
in outline, with well-rounded lateral extremities and truncated anterior margin. 
Surface costellate with 2 to 5 costellae occupying the sulcus and 3 to 6 on the 
fold. Costellae on flanks variable in number, generally about Io. 
Pedicle valve most convex in the posterior half, flattened or gently convex in 
the anterior half. Sulcus originating slightly posterior to the middle, moderately 
deep, and occupying about half the width at the front of the valve. Tongue mod- 
erately long. Flanks bounding sulcus gently convex; lateral slopes moderately 
steep. Hinge width equal to or slightly less than half the shell width. Interarea 
short. 
Brachial valve very strongly convex in lateral and anterior profiles. Umbonal 
region not prominently swollen; beak not extending beyond posterior margin. 
Fold originating about one-third the length from the beak, only slightly elevated 
above the flanks throughout its length. Flanks most convex near the fold and 
with steep slopes to the margins. 
Measurements in mm.— Brachial Hinge 
Length length Width width Thickness 
Holotype (pedicle valve)....... 10.5 ? 12.4 ? ? 
Hypotype (123296a) .......... 9.0 8.1 10.3 6.8 6.5 
us GEPGEOSD)) Gis. weiss 10.0 9.8 12.8 6.7 6.3 
